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Groups > comp.lang.c++ > #82503
| From | Bonita Montero <Bonita.Montero@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: equal_range sucks ! |
| Date | 2021-11-28 17:04 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <so09ao$46m$2@dont-email.me> (permalink) |
| References | <snivjr$afv$1@dont-email.me> <snvpjf$14uo6$1@gwaiyur.mb-net.net> |
Am 28.11.2021 um 12:36 schrieb Marcel Mueller:
> Am 23.11.21 um 15:59 schrieb Bonita Montero:
>> I just tried this:
>>
>> pair<cpu_it, cpu_it> foundApicId = equal_range( apicIds.begin(),
>> apicIds.end(),
>> apicId, []( cpu_apic_id const &idRange, unsigned apicId ) {
>> return idRange.apicId == apicId; } );
>>
>> It should be possible that the key for the range has a different type
>> than than the elemnens in the range so that I can compare against a
>> part of the range-objects like in the above code.
>
> Feel free to write an asymmetric comparer that fits your needs.
>
> You may also implement an asymmetric operator<, but implicitly comparing
> apples with oranges is not a good advice.
I've written an asymmetric version:
template<typename RandomIt, typename T, typename Pred>
std::pair<RandomIt, RandomIt> xequal_range( RandomIt begin, RandomIt
end, T const &key, Pred pred )
requires std::random_access_iterator<RandomIt>
&&
requires( Pred pred, typename
std::iterator_traits<RandomIt>::value_type &elem, T const &key )
{
{ pred( elem, key ) } -> std::convertible_to<std::strong_ordering>;
}
{
using namespace std;
assert(end >= begin);
size_t hit = -1, lower = 0, upper = end - begin, mid;
strong_ordering so;
while( lower != upper )
{
mid = lower + (upper - lower) / 2;
so = pred( begin[mid], key );
if( so >= 0 )
{
if( so == 0 )
hit = mid;
upper = mid;
}
else
lower = mid + 1;
}
if( hit == -1 )
return pair<RandomIt, RandomIt>( end, end );
begin += hit;
hit = 0, lower = 1, upper = end - begin;
while( lower != upper )
{
mid = (lower + upper) / 2;
so = pred( begin[mid], key );
if( so > 0 )
upper = mid;
else
assert(so == 0),
hit = mid,
lower = mid + 1;
}
end = begin + hit + 1;
return pair<RandomIt, RandomIt>( begin, end );
}
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equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 15:59 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 16:04 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 17:13 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 19:53 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-25 15:02 +0100
Re: equal_range sucks ! Juha Nieminen <nospam@thanks.invalid> - 2021-11-24 08:06 +0000
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-24 18:18 +0100
Re: equal_range sucks ! Marcel Mueller <news.5.maazl@spamgourmet.org> - 2021-11-28 12:36 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-28 17:04 +0100
Re: equal_range sucks ! Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-28 17:23 +0100
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